class fa {
    constructor(x, y) {
        let num = Math.pow(x, y)
        console.log(num);

    }
    outx() {
        console.log("s" + this.x);
    }
}
class son extends fa {
    constructor(x, y) {
        super(x, y);
        this.x = x
            // this.y = y 
            // 不定义会找不到
    }
    out2() {
        console.log("2" + this.y);
    }

}
var sonh = new son(2, 4, 5)
sonh.outx()
sonh.out2()